Abstract: In this paper, wake electron density of hypersonic sphere models has been measured in ballistic range, CARDC.The electron density measurement system is made up of 8mm micro-wave interferometer, open microwave cavity measurement system and closed microwave cavity measurement system.The diameter of the steel sphere models is 10mm.The model velocities are 5.8, 5.5, 5.6 and 5.5km/s. The corresponding flight environmental pressures are 2.79、5 32、 5.85 and10.91kPa.The diameter of copper sphere models is 10mm.The results present the wake electron density of steel sphere models is larger as a result of high environment pressure under the test conditions of the pressure ranged from 5.3kPa to 11kPa, speed 5.5km/s.The composite speed is quick under the conditions.The wake electron density of copper sphere models is larger as a result of high environment pressure under the test conditions of the pressure ranged from 1.3kPa to 6kPa, speed 5.6km/s test conditions. The composite speed is slow under the condi-tions.The composite speed of copper sphere models is slower than that of the steel sphere models under the conditions of the pressure 10.7kPa and speed 5.5km/s.